An Energy-Efficient Readout Method for Piezoresistive Differential Pressure Sensors

Abstract

This paper describes a low power and low noise circuit for resistive Wheatstone bridge sensor readout. The proposed readout exploits the bridge configuration of the sensor by embedding it into a second-order continuous-time sigma delta modulator (RC CTΔΣM). By directly digitizing the output signal of a Wheatstone bridge in the current mode, the noise performance is dominated by the operational transconductance amplifier (OTA) in the first integrator. The proposed readout is designed in a 0.35 μm CMOS technology. Simulation results show that it achieves an input referred noise power spectral density (PSD) of 4.2 nV/√Hz with a current consumption of 860 μA from a 5 V voltage supply. This represents a noise efficiency factor (NEF) of 4.7.